The present invention is related at least generally to helicopter control systems and, more particularly, to an emergency collective actuator having a friction pull-off and associated method for a helicopter.
It is recognized in the prior art such as is exemplified by U.S. Pat. No. 4,667,909 (hereinafter the '909 patent) that a sudden power failure during the flight of a helicopter requires the immediate attention of the pilot to convert to autorotation by lowering the collective pitch of the main rotor blades of the helicopter. A failure to timely reduce the collective can result in stalling the rotor blades. Such stalling of the rotor blades will generally produce a catastrophic crash wherein the helicopter, quite literally, falls from the sky. One example of such an accident, which likely involved a rotor stall, occurred in the United Kingdom in March of 1998 and is the subject of AAIB Bulletin no. 11/98. Such an accident will generally be fatal to anyone onboard the aircraft. The particular helicopter that was involved in this accident was the Robinson R22, which is a lightweight helicopter having a low-inertia rotor system. It should be appreciated that a low-inertia rotor system can be stalled more easily than a rotor system having a greater level of inertia. The subject accident report outlines operational conditions for the Robinson R22 under which rotor speed will decay to an unrecoverable value in less than 1 second during a climb.
As a solution, Applicant developed an emergency collective pull-down apparatus that is described in U.S. Pat. No. 8,360,369 (hereinafter, the '369 patent), issued Nov. 23, 2010, and U.S. Pat. No. 8,651,425 (hereinafter, the 425 patent), issued May 23, 2012, each of which patents is hereby incorporated by reference. The disclosed apparatus, of the '369 and '425 patents, applies a collective pull-down force directly to the collective control. While the '369 and '425 patents represented a significant leap in the then-existing state-of-the-art and continue to provide benefits in terms of enhancing flight safety in a light helicopter, Applicant now brings to light an emergency collective actuator which provides still further benefits.
The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.